Solvent extraction process for separating ionic compounds

ABSTRACT

METATHESIS REACTIONS BETWEEN WATER SOLUBLE IONIC COMPOUNDS ARE CARRIED OUT BY MEANS OF A LIQUID EXTRACTION PROCESS USING WATER AND A MIXTURES ORGANIC SOLVENT. THE SEPARATION OF MIXTURES OF WATER SOLUBLE SALTS ARE ALSO CARRIED OUT USING WATER AND A WATER MISCIBLE ORGANIC SOLVENT.

1.. J. BECKHAM 3,808,308

SOLVENT EXTRACTION PROCESS FOR SEPARATING IONIC COMPOUNDS April 30, 1974 6 Sheets-Sheet 1 Original Filed Nov. 17, 1967 mmmmD NIP m0 ZOTEWOQEOU U +0". I QI z m ozfz April 30, 1974 L. J. BECKHAM 3,898,303

SOLVENT EXTRACTION PROCESS FOR SEPARATING IONIC COMPOUNDS 6 Sheets-Sheet 2 Original Filed Nov 17, 1967 ow o on on #OWNQ2W on I 0m 3 I v 0* w xm ET I on 2 m o om oz z 62+: 2 on 00 0+ on P 1974 L. J. BECKHAM 3,808,308

SOLVENT EXTRACTION PROCESS FOR SEPAHATING IONIC COMPOUNDS 6 Sheets-Sheet 3 Original Filed Nov. 17, 1967 ON 6 Ow O0 omz-zw 6 I QIZVM OQ|.. HON OQII MO? 01 o 0 M... 60E 6! 6 :2

April 30, 1974 L. J. BECKHAM SOLVENT EXTRACTION PROCESS FOR SEPARATING IONIC COMPOUNDS 6 Sheets-Sheet 4 Original Filed Nov. 17, 1967 N ON 0* 00 on Ow ON Ow 0 xm O 00 3 w QE 3 b2 Iz Om Om 0+ ON April 30, 1974 L. J. BECKHAM SOLVENT EXTRACTION PROCESS FOR SEPARATING IONIC COMPOUNDS 6 Sheets-Sheet 6 Original Filed Nov 1'7, 196'? ON 0 OO O N m N W m Q V W OQ ON mm xm 4 o? J 3 2T 9 xm -8 D 0 ON OQ z 00 Ow 0? ON un te smes Patent ABSTRACT OF THE DISCLOSURE Metathesis reactions between water soluble ionic compounds are carried out by means of a liquid extraction process using water and a water miscible organic solvent. The separation of mixtures of water soluble salts are also carried out using water and a water miscible organicsolvent.

This is a divisional application of my copending application Ser. No. 683,878, filed Nov. 17, 1967, now U.S. Pat. 3,635,661, patented Jan. 18, 1972.

BACKGROUND OF THE INVENTION This invention concerns a new method for carrying out a metathesis reaction involving water-soluble ionic salts and it also concerns a new method for separating a mixture of water-soluble salts.

When two or more ionic compounds are dissolved in water, an equilibrium mixture of the ionic components usually results; and in order for a metathesis, or double decomposition reaction involving ionic compounds to proceed to completion in solution, one of the products must be removed from reaction in order to upset the equilibrium. Thus, a metathesis reaction between ionic compounds proceeds to completion in solution if one of the products precipitates from the solution due to its insolubility', escapes from the solution as a gas, or is nonionizable and thereby removed from the ionic equilibrium. However, it is difficult to carry out a metathesis reaction to completion in solution when both the starting materials and the products are water-soluble ionic compounds and in many cases no known method is available. In some instances, by working at two dilferent temperatures and alternately crystallizing first one and then the other of the predominate salt pair, i.e. the two salts which crystallize out preferentially in a system containing four ionic species, it is possible to complete a metathesis reaction involving two water soluble salts in the direction of the predominant salt pair. This technique is illustrated, e.g., in the reaction:

in Aqueous Solution and the Phase Diagram by Perdon and Slater (Arnold and Company, London, 1946), pp. 110118. This method is applicable only for carrying out reactions in the direction of the predominate salt pair and only when there is a reasonable diflference in relative solubility with temperature of the product salts.

SUMMARY OF THE INVENTION An object of the present invention is to provide a new method for carrying out a metathesis reaction between ionic compounds. Another object of this invention is to provide a method whereby a metathesis reaction between water-soluble salts can be carried out substantially to completion in solution. Another object of the invention is the provision of a method by which a metathesis reaction between water-soluble components can *be carried out in either direction; e.g., when a system has a pre- I dominate 'salt pair, the pair may be either reactants or V X from said reaction zone.

products.- A further object of this invention is the .provi sion of a new process for preparing water-soluble alkali. metal salts, including ammonium salts. A still further object of this invention is the provision of a simple and economical method for separating a mixture of water-- soluble salts. It has now been discovered that a metathesis reaction between two water-soluble salts can be carried out substantially to completion by means of a countercurrent liquid-liquid extraction involving water and a water miscible organic solvent. The present invention involves a method forcarrying out a metathesis reaction according, to the equation:

wherein M and V are different monovalent cations, X is a polyvalent anion, Y is a monovalent anion and M X," VY, V X and MY are each water-soluble salts, and n is an integer of 2 to 5 which comprises:

(a) Introducing M X and water into a reaction zone;

(b) Introducing VY into said reaction zone at a pointremote from the introduction of M X;

(c) Introducing a water-miscible organic solvent into. said reaction zone at a point remote from the introduction of M X;

1 (d) Passing said M X and water countercurrent to and; into intimate contact with said VY and said organic solvent in said reaction zone, to effect a net'flow of anion- X opposite to the net flow of anion Y and to maintain. a sufiicient concentration of M X and VY in the resultant mixture of water and organic solvent to cause formation. of two liquid phases, a phase rich in said organic solvent and a phase rich in water, whereby anion Y is selectively: extracted in the organic solvent-rich phase and anion X is selectively extracted in the water-rich phase;

(e) Withdrawing said organic solvent-rich phase con taining MY- from said reaction zone; 3 v v (f) Withdrawing said water-rich phase-containing a BRIEF DESCRIPTION OF THE pmwmos FIGS. 14 arediagrams which ,show the-distributi of the indicated ionic components, expressed iinequivalents, in each of the two phases of a systemcontaining water, a water miscible organic solvent and the indicated; salt mixture. As discussed in detail he reinafterfthe upper. point normally designates the ionic composition of the, organic solvent-rich layer and the lower point the corn-, position of the aqueous phase. In FIGS. 1 an 2, asingle system has been diagrammed which contains the four. v indicated ionic species, water, and an organic salv na; In'FIGS. 3' and 4, the effect of ditferentor ganic,solvents on the distribution of the indicated salt system islillus trated, each line representing the distribution ofthe'io ns in a dilferent organic solvent-water mixture. FIGSUSQI and 6 are each diagrams which show the 'dISti'ibUIiOn Of:, ionic components, in equivalents, l obtained,in each, of the. productstreams by carrying out the indicated i'ijet athesis reaction 'in .accordance with this invention, "but ',u'sing,.', different numbers of extraction stages, in..FIG.. 5,

droxane,

I. fmethanol, dimethyl sulfoxide; piperidine, 'tertiary" butyl-' amine, dimethylformamide and mixtures of these solvents,

Isopropyl alcohol is an especially preferred solvent in this process due to its solubility characteristics and low cost. The cations M and V are monovalent ions such as sodium (Na+), potassium (10*), ammonium (NH,+) or lithium (Li+). The anion Y is a monovalent water soluble anion, for example, fluoride (F-), chloride (Cl-), bromide (Br), iodide (1-), nitrate (NO monobasic phosphate (H POF), acetate (CH COO), for'mate I-ICOO-) or thiocyan'ate (SCN'); and the anion X'is a water-soluble polyvalent anion, i.e. an anion having a valency of two to five, such as dibasic phosphate (HPO,=), carbonate (CO thiosulfate (5 sulfate (SO,=), dibasic pyrophosphate (H P O tribasic tripolyphosphate H,P,0,, dibasic citrate -(C H O tribasic citrate (C H O tetrabasic tetrapolyphosphate (112F401?) tribasic pyrophosphate (HP OF), tetrabasic tripolyphos phate and pentabasic tetrapolyphosphate herein as the organic solvent-rich phase. It has been found that under these conditions the polyvalent anion X is selectively extracted into the water-rich phase and the monovalent anion Y is selectively extracted into the organic solvent-rich phase. This process is carried out so that the organic solvent-rich phase flows countercurrent to the water-rich phase thus effecting a net flow of anion Y in a direction opposite to the net flow of anion X.

In accordance with this invention, to obtain the products V,,X and MY, the starting material VY is introduced into the reaction zone at a point or points remote from the "introduction of the starting material M X. Using a split feed, separation of the cations V and M is obtained by reason of the following. The anions X and Y are moving in opposite directionsdue to selective extraction in the'ltwo countercurrent liquid phases. The monovalent cations'v and M have substantially no'net motion since theygene'rally have similar solubility characteristics in the twophasesfand, therefore, they showlittle or no relative distribution in the system. However, there is a definite gradient of cationdistribution when the introduction of VY is remote from the introduction of M Y, since the 'concentrations of Mand V are then greatestat the respective points of introduction. Thus, the organic solventrich phase which contains the monovalent anion Y is fedat a point remote from the introduction of M x, and since the organic solvent-rich phase moves in a direction opposite to that of the water-rich phase, it, is withdrawn at a point near the introduction of M X where the concentration of the cation M is highest; the organic solvent-rich extract thereby contains the product MY. 'Ih'e',water-rich phase containing the polyvalent anion X, moving in the opposite. direction to that of the organic solvent-rich phase is then withdrawn nearvthe point of introduction of the compound V'Y where the concentration of the cation V is greatest; the water-rich extract thereby contains the product V X. It is understood that each ofthe starting-materials, i.e. M 'X, VY, water and organic solvents maybe introduced from one was many points in the .system as is considered desirable, as long as the introduction of the reactant salts is at points-remote from each other and the two resultant liquid phases move 1 in a countercurrent direction to one another.

A rich phase, while the monovalent anion is selectively ex--.. tracted into the organic solvent-rich phase. Byseparation In 'th'e reaction zone some separationo'f the anions X and Y occurs, but the primary purpose of the reaction zone is to elfect separation of the cationsM' andV. In order to further or complete the separation of X and Y, the solvent-rich extract containing the product MY may be passed into a polyvalent anion stripping zone wherein the organic solvent-rich phase is intimately contacted with a countercurent stream of a salt solution, preferably a reflux stream of the product MY after removal of all or part of the solvent. Likewise, the aqueous, extract containing the product V,-,X may be passed into a mono-; valent anion stripping zone wherein the aqueoussphase is intimately contacted with a countercurrent stream of the organic solvent or preferably of its mixture with water.

Alternatively, or in addition to the stripping zones, the product solvent streams can be furtherpurified or concentrated by conventional crystallization procedures and by well-known distillation procedures.

The following equations exemplify reactions which can be carried out according to this process:

According to another aspect of the instant invention, a mixture of water-soluble salts is separated into salts containing monovalent anion'and salts containing divalent or. polyvalent anion by dissolving the salt mixture in a solvent composed of Water and a water miscible organic solvent. Two liquid phases are thereby formed; a phase I rich in water-and a phase rich in organic liquid (but not necessarily more organic liquid than water), and the polyvalent: anion is selectively extracted into thewaterof the phases and repetition of the process, either as a batch or continuous countercurrent liquid-liquid extraction, substantially complete separation of the salt mixture into salts containing monovalent anion and salts containing divalent or polyvalent anions is obtained, substantially without separation of cations.

In a similar manner, if it is desired to carry out a partial metathesis reaction, without separation of the cations, as for example the preparation of ammonium-potassium hydrogen phosphate fertilizer from potassium-chlo-' ride and diammonium phosphate, the starting materials are fed together into a mixture of water and watermiscible organic solvent and the products are obtained by separating the two liquid phases which form.-Thus, if it is not important to separate the cations, the starting materials may be fed into a central stage of the countercurrent extraction. i

The process of this invention can be carried'out either as a batch or a continuous operation. Any apparatus suitable for countercurrent liquid-liquid extraction can be used including mixer-settler type equipment and continuous contact equipment, such as gravity-type columns, for example, spray towers, packed towers, and mechanically operated columns, such as pulsed columns and rotary-type columns, and centrifugal extractors such as Podbielniak extractors.

As in any extraction process, the degree of separation depends on the number of stages in the extraction and the strength of the separating force. The strength of the separating force varies greatly with the ionic components involved, and to some extent with the solvent system and the salt concentrations employed.

The strength of the separating force of a system is found by dissolving substantially equivalent proportions of the ionic components in a mixture of water and the chosen water-miscible organic solvent, separating the two phases thus formed, and determining the concentration of each ionic component in each phase. Several such determinations are illustrated in examples and the results of a few of these determinations are diagrammed in FIGS. 1-4, respectively.

FIGS. 1- 2 are diagrams which show the distribution of the indicated ionic components, expressed in equivalents, in each of the two phases of a system containing water, a water-miscible organic solvent, and the indicated salt mixture. If the four ionic components are mixed in equivalent amounts, this starting mixture would be represented by a point at the center of the diagram. The compositions, expressed in ion equivalents are plotted in what is generally described as a reciprocal salt pair diagram (Janecke Projection, p. 439 and the reference'to Table 17-1 (g), p. 434, The Phase Rule and Heterogeneous Equilibria by John E. Ricci, D. Van Nostrand Co., Inc. (1951)). By convention, the starting salts are always designated at the upper right-hand corner and lower lefthand corner of the diagram. The upper point designates the ionic composition of the lighter, organic solvent-rich layer and the lower point the ionic composition of the heavy aqueous phase. By joining the points with a line 60 as shown, and called hereinafter the distribution line, and

observing its length and inclination, one obtains a good' understanding of the system and can estimate the number of extraction stages required to obtain the degree of separation required, e.g., substantially complete metathesis if desired. Thus,the greater the vertical separation of the endpoints, the greater is the separation or distribution of. the anions in a single-stage extraction. The inclination of' the desired products indicates that a greater number of extraction stages are required. However, .unless the inclination is very great, approaching 45, the reaction 6 v can be conducted in such way as to make either-of the products. I i 11 Wherethe distribution of the ions in a particular solvent mixture is unfavorable for carrying out a metathesis re action in the desired'direction, a better distribution is often obtained by using a different organic solvent." The eifect of .using different solvents has been illustrated in FIG'S."3*and'"4. In FIG. 3,'the distribution of theions (K+), (Cl), (NHJ), and (HPOE) in a variety of or ganic solvent-water mixtures has been plotted. The distribution lines show that the reaction h a can be carried out in either direction using any of the illustrated solvent systems in the process of this invention except piperidine and possibly tertiary butylamine. With those two solvents, the reaction can be carried out very readily in the direction of making K flPO There is a substantial difference in the distribution of the ions in different systems and hence a difference in the ease of reac-- tion, :i.e., number of extraction stages required to carry out any particular metathesis-reaction depending on the chosen organic solvent. As shown in FIG. 3, using an isopropyl alcohol-water mixture in the process of this invention; the reaction may be carried out to the right or the left with about equal ease; the slightly inclined distribution lines show that this is also true for a dimethylsulfoxide, dioxane, dimethyl-formamide, or'fi-ethoxyethanol-water mixture. However, this reaction is carried out may be carried out in either direction and that it may be carried out to the right slightly more readily using a mixture of water and ethanol and slightly more readily to the left using a methanol-water mixture.

While it has not been possible to determine rigorously the exact number of stages required to carry out a particular reaction to a specified extent, due to the fact that at each' extraction stage both the concentration of the a system is close to one, the system usually can be improved.,by.changing the salt concentration, the proporfour ionic species and the proportions of organic solvent and water change in the two phases, it is possible totreat mathematically the analytical data obtained and to derive an index showing relative separating strength of the system. In the system and the index for making M X and VY is expressed as wherein C 0,, C CL represent the ionic concentrationsin milliequivalents per grams of layer with the superscrips u and! indicating upper and lower layers, respectivelyajAn index of one is the limiting case where noj separation occurs; the larger the index the better the separation and the fewer the number of extraction stages,

required for any desired degree of reaction.

In the event the index for a single-stage extraction of tion of "organic solvent and water in the system and/or. as already discussed, the organic solvent.

'However, it has been found in general that the strength I of the separating force of water, water-miscible organic solvent'systems containing monovalent metallic cations,

including ammonium ion, a polyvalent anion and a monomaking V X and MY is expressed as valent anion is sufliciently high to effect a good degree of separation of the desired-products if at least three extraction stages are used. In some cases, however, if substantially complete separation is desired, it may be necessary to use thirty or forty extraction stages. To effect a substantially complete metathesis reaction of the type described'herein with reasonable economy, of the order of 5 to 25 extraction stages are generally preferred; by extraction stages it is understood that the stages may be actual or theoretical stages.

The reaction of potassium chloride and diammonium phosphate in a mixture of water and isopropyl alcohol, for example, -is substantially complete when. a 19-stage reaction zone is used in combination with chloride and phosphate stripping zones. In FIG. 5 the degree of reaction of potassium chloride and diammonium phosphate, in a water isopropyl alcohol mixture using reaction zones with different numbers of stages and with and without stripping zones is compared. It is found that the reaction is proceeding in the desired direction, but is incomplete" when a 3'-stage reaction zone is used, and that substantially complete separation of the cations and-anions is obtained using a 19-stage reaction zone together with stripping zones. In FIG. 6, the use of a 1 and 5 stage reaction section respectively to effect the reaction of potassium chloride and diammonium carbonate using water'and isopropyl alcohol has been diagrammed. It is seen that the separation of the potassium and the chloride ions is nearly complete using a S-stage reaction section. V

The process of the invention is conveniently carried out at ambient temperatures although higher or lower' ture, and the salt concentration can range up'to the saturation point. The effectiveness of a system changes somewhat at diiferent concentrations, and for any given system, a particular range of concentration is most advantageous; however, for reasons of economy, it is'usually preferable to work with relatively concentrated, solutions. Therefore, it is preferable to carry out the process. wherein the salt concentration in the reaction zone is at least 5 parts by weight per 100 parts by weight of the solvent mixture. -The most favorable proportion of the organic solvent in the reaction zone also depends on the particulars'ys tem undergoing *metathesi's; about 25 to 400 parts by weight of organic solvent per l parts by weight of water -can be used in this process; however, the preferred proportion of organic solvent is on the order of 30 parts to 200 parts by weight of organic solvent per 100 parts by weight of water. The parts of solvent for; 100 parts of water preferably should exceed that at the plait point,

i.e., the composition at which the two conjugate layers of the system become identical.

The salt, in a few instances,'does not efiect a separation of the solvent mixture into two phases. Thishappens either because the salt is present in-insufi'icient concentration, which occurs particularly in'the polyvalent anion stripping zone of the extraction, or because of its poor salting out characteristic. In any case, thelackof two phases in a'system may be corrected bythe-addition of a minor amount of a water-immiscible-solvent, usually a liquid hydrocarbon or even. by -the addition of another salt such as, e.g., NaCl. Since the system is normally close to separation into two;phasesdue to the presence of the salt mixture, only a minor amount of hydrocarbon, of the order of 0.1 to percent by,

weight of the solvent mixture, usually needs to be introduced. into the reaction zone, though occasionally some=;

what larger amountsfup to about or 20 percent by weight of the solvent mixture may be added to a stripping zone.

In one manner of carrying out the process of this invention in a reaction zone containing n number of extraction stages, water and the polyvalent anion-containing salt are fed at stage 1 of the reaction zone. The salt can be introduced in any manner which is convenient; a common method is to premix the salt with water and to introduce it into the reaction zone at the desired con centration. If the'process includes a polyvalent anion stripping zone, the water-rich phase from the stripper, containing the polyvalent anion salt and minor quantities of monovalent anion salt from the water-miscible organic solvent is returned to the reaction zone at stage 1. The monovalent-anion salt is fed into the reaction zone at stage n, and the water-miscible organic solvent is also introduced at stage n. The monovalent-anion salt is also introduced in any convenient manner, for example, in granular form, as a slurry, or in solution. In most instances it has been found necessary to introduce water at stage n in addition to the organic solvent in order to obtain the proper salt distribution in the layers; and sometimes, a minor amount of the water-miscible organic solvent is introduced at stage 1 of the reaction zone. Maintenance of liquid-liquid countercurrent extractions at a steady state, i.e., wherein the rate of withdrawal of the solvents from the extraction is approximately the same as the rate of introduction, is usually desirable. In addition, if the aim is to isolate two substantially pure products from the metathesis reaction, an excess of one reactant in is to be avoided, and it is also desirable to run the extraction process balanced with respect to the net flow of polyvalent anion and monovalent anion. Surprisingly, it has been found in practice, that in order to maintain most extraction systems of this invention in balance with respect to the net flow of the solvents and with respect to the net flow of the anions, while the water-rich phase flows countercurrent to the organic solvent-rich phase, usually the net flow of both water and organic solvent is from stage n to stage 1. Thus, it is found that while the exact proportion of water and organic solvent in each phase varies at each stage, in general, the heavy, water-rich phase contains only a minor quantity of organic solvent, whereas the light, or-ganic' solvent-rich phase contains, in addition to most of the organic sol-' vents, substantial quantities of water, in some instances even exceeding the quantity of organic solvent. If thesystem is operated with a monovalent anion stripping zone, water and the water-miscible organic solvent may be added to a stage in the monovalent anion stripping zone. The organic solvent-rich phase from the stripping zone which is then introduced at stage n of the reaction zone contains water, monovalent anion and a lesser quantity of'polyvalent anion.

Generally, the monovalent-anion containing salt and the polyvalent anion containing salt are introduced into the reaction zone in approximately equivalent propor-- tions, the rate being such as to provide a salt concentration of at least 1 part and preferably about 5 to 15 parts per. parts of total solvent in the reaction zone.

-.However, in certain processes where only one product is of interest, the proportions of reactants maybe varied. According to this invention, a metathesis reaction can alsobe made to .takeplace between two water-soluble ionic compounds where there is little or no separation or distribution of the cation or anion pair in the two valent which may be represented by the equation:

wherein V and M are dilferent monovalent cations, Y and Z are different monovalent anions, VZ, MZ and MY are watersoluble salts, is successfully carried out by adding M X to the system, wherein M X is a watersoluble salt, M is a monovalent cation, and X is a divalent or polyvalent anion. In accordance with this innVY-i-nMZ-mMY-l-nVZ (HI) Furthermore, the two reactions can be run consecutively in two countercurrent extraction systems, or they can be carried out together in different zones of the same system. In the latter case, M X and V X are continuously withdrawn from different points and reintroduced at the proper stages of their respective reaction zones and,

thus, effectively never leave the system.

The following examples describe specific embodiments of my invention and illustrate the best method contemplated for carrying it out, but they are not to be interpreted as limiting the invention to all details thereof, since changes can be made without departing from the scope or spirit of the invention. Parts and percentages are by weight and temperatures are in degrees centigrade.

The first 23 examples demonstrate the feasibility of operating the process of-the invention with the particular salts and solvents systems. These examples are important as indicating the effect of a single extraction stage and permit a judgement on the number of stages required to extend this separation, i.e., effect a complete metathesis reaction or to effect the degree of separation desired. In each of these 23 examples, an index (I) indicating the separating strength as previously discussed, is determined for reaction in either direction.

THE SEPARATION OF SALT MIXTURES Example 1 Analysis: Milliequivalents per 100 grams of layer m( 4 y( v (I?) x( 4') Upper layer Lower layer The composition of the two layers has been diagrammed graphically in FIG. 3.'

Lower layer- Equivalent ratio Upper layer Cations; Anions.

g p Example 2 l Potassium. fluoride, 13.1 grams, and diamrn'oni'um phosphate," 14.9 grams, were dissolved in 100 grams: of water, and 100 grams of ethyl alcohol were added. After shaking, the mixture was allowed to separate into two liquid layers. The upper phase weighedv 166.9 grams; the lower phase weighed 58.3 grams. Analysis of the phases gave the following results.

Analysis: Milliequivnlents per 100 grams of layer Cm(N 4 ym) H CAHPOF) Upper layer 35. 5 59. 7 28. 2 j 4. 0 Lowerlayer 275 208 298 365 'Derivation of index number Equivalent ratio Upper layer Lower layer 44/56 52 48 93/7 36/64 Example 3 Analysis: Mllliequivalents per 101] grams ofilaye'r Cm(NH4+) c,, F c.(x c.(Hoo- Upperlayer 55.6 "41.1 37.4 i, 51.9 Lowerlayer 149.0 171.2 183.8 151.6

MXj+VY VX+MY Nrnooon KCl KOOCHNHiCI E ;55.s 41.1 183.8 161L6 14Q 171.2 37.4 51.9; g MX'+VY VX+MY NILOOCH KCI KOOCH NHiCl 1 I: 37.4 41.1 149 161.6 =0

Equivalentratio. -L; Upperlayer l' Lower layer Cations 40/60 E 55(45 Anions "Cl-H600 '44 56 i 51 /49 This test shows that the two r'nonov'alent. anions 'have little or no tendency to separate frorneach other in the two liquid layers. i 1i i Examples 4-23 have been carried: out in the same manner as Examples 1 and 2; the starting materials and the results have been tabulated in Table I.

15 however, that if substantially complete separation is desired, additional stages would be required.

Example 25 This reaction was carried out in three stages in the manner described in Example 24 except that the reactants were ammonium chloride and dipotassium phosphate.

The aqueous feed introduced at state 1 contained 225 inilliequivalents (19.6 grams) of K HPO 8 grams isopropyl alcohol 100 grams water.

The organic solvent feed introduced at stage 3 contains:

225 milliequivalents (12.1 grams) of NH CI 92 grams of isopropyl alcohol 100 grams of water.

The product streams were analyzed after the sixth cycle and the results are set forth and compared to the compov sition of the feed streams in the table below. The results show that the reaction is going in the desired direction; Comparison with Example 24 indicates that this reaction can be carried out in either direction with about equal effectiveness. Y

Composition of light Y i organic solvent-rich (lomposltlon oi heavy phase water-rich phase With- Intro- With-e :Intro- 5 T; drawn at dueed at drawn at duped at stage 1 stage 3 1 stage 3 stage 1 Total quantity of ions v 1 (milliequivalents) i N Hfi' 61 225 136 0 171 0 J 57 225 160 225 N 47 0 :72 o n 146 225 o so 00', 14 100 o 71/25 15 HCOO-IHPO 69/81 '100/0 24/76 5 1 Not analyzed. l v 1 Example 27 v l- This reaction: was carried out in the manner described in Example 24 except that the reactants were sodium nitrate and ammonium sulfate and the organic solvent was acetone. I i I The aqueous feed introduced at stage lgcontain'edfi 16.5 grams (250 milliequivalents) (NI- LJgSOa.

50 grams waterl I 10 grams acetone.

30 The solvent feed introduced atstage 3 contained: 21.2 grams (250 milliequivalents) Na'NO 80 grams water f Compositinn oilignlt C t h I 40 grams n r or amc so ven -r1c omposi ion 0 ea j I F g phase water-rich phase The product streams were analyzed after the 7th cycle with 11mm With Intro and the results are set forth and compared to the feed drawn at duced at drawn at duced at streams in the table bElOW. f 5;

Stag Stages Stag 81561 The results indicate that the 3-stage operation fiwaslef- Total quantity oiions fective in separating the NH and Na cations, although fi qmvalents)- 48 225 183 40 additional stages would be required to obtain substantial- 139 o 75 225 ly complete separation, and an .increase'in the rati'o -rof HPOF {5g 2 Water to acetone would be necessary to obtain more equal Total quantity ot- 8 1 n i quantities of the two products. Also this example demoniZ TE$i a 1LEEai 14 00 48 a strates the effectiveness of acetone as a solvent. E m (glrams)t 97 92 7 8 q 8mm 1 r l Com osition o ii ht Hr /K 26/74 100/0 71 29 0 10 v. or 8 game solventch Compositlomof hee. o1 /HPO4 59 41 100 o 47 53 0 10 phase which With- Intro Witliintrodrawn at dueed at drawn at duced at stage 1 stage 3 stage 3 stage 1 Total quantity of ions I 1 Example 26 (milliequivalents):, v v .1 I.

NH4+ 224 0 13 250 202 .250 7e 1 0 2HCOONH +K HPO 2HCOOK+ (NH HPO fig. 25gv g3 8 This reaction was carried out in the manner described 3? S 28 is in Example 24 except that the reactants were ammonium H VN 0/1 11 1 I.

a a 47 00 5 s5 100 0 formate and dipotass um phosphate. Nogvsorun 58/42 7 100/0 if {0/160 The aqueous feed introduced at stage 1 contained: M p 19.6 grams (225 milliequivalents) of K HPO y 1e I 80 grams Water- K C H QH-3NH C1 (NH C H Q1+ 3Kci. i. The or anic solvent feed introduced at sta e 3 contained: i F

g g v This reaction was carr ed out.. 1n the manner, descr bed 14.3 grams 225 milliequivalents) of ammonium formate 1n Example 24 except the reactants were ar nmoniumchlo- (HCOONH 1 100 grams of water 100 grams isopropyl alcohol.

The product streams were analyzed after the 7th cycle and the results are set forth and compared'to the feed streams in the table below. It can be seen from this data that the reaction of K HPO with ammonium formate is comparably as efiective as was the reaction with ammonium chloride in Example 25. v i

' ride and tripotassium citrate. i The aqueous feed introduced at stage 1 con ained:

100 milliequivalents' tripotassium citrate (prepare jd from 7.0 grams citric acid hydrate and 5.6-gra'1i1s KQH)L 25 grams waters The solvent feed introduced at stage 3 contained:

100 milliequ ivalents"ammonium chloride (5135 50 grams water j E 75 grams isopropyl alcohol; "1

17 The product streams were analy'zedaft'er the 5th cycle and the results are set forth and compared to' 'the'feed streams in the table below. Goodseparation of NH and Kt cations was achieved but more stages would be requiredfor substantially complete separation. This ru'n also demonstrates the applicability of the'pr'ocess of this invention to a trivalent organic anion, the trivalent citrate.

Composition oi light organic solvent-rich Composition of heavy phase water-rich phase With- Intro- With- Introdrawn at duced at drawn at duced at stage 1 stage 3 stage 3 stagel Total quantity of ions (milliequivalents) NH? 13 100 87 K 36 0 58 100 Cl- 31 100 68 0 CeHsO 18 0 77 100 Total quanti H2O, grams 50 50 30 25 Isopropyl alcohol 71 75 1 0 Equivalent ratios:

N Er /K 27/73 100/0 v60/40 0/100 Cl-/CtH O 63/37 100/0 47/53 0/100 Example 29 This reaction wascarried out ihe manner deseribedin Example 24 except that the reactants were potassium 111 1- oride and diammonium phosphate.

The aqueous feed introduced at stage 1 contained: 150 milliequivalents (NHQHPO, (9.9 grams) 25 grams water.

The solvent feed introduced at stage 3 contained: 150 milliequivalents KF (8.7 grams) 100 grams water 100 grams ethanol.

The product streams were analyzed after the third cycle.

and the results are set forth and compared to'the feed" streams in the table below.

The results indicated that the'3-stage operation was e f fective in separating the NH and K+ cations, although additional stages would be required to obtain substantially complete separation.-Moreover, the example indicates that ethanol is an effective solvent. Furthermore, it ap-v pears that the system had not quite reached steady state at the end of the 3d cycle and one or more additional cycles would have been required to do so.

Composition of light organic solvent-rich Composition 0! heavy This reaction was carried out in the manner described in Example 24 except that a mixture of methanol and isopropanol was used as solvent. 7 v

The aqueous feed introduced at stage 1 contained:

14.9 grams (NH H=PO (225 100 grams water 58 grams isopropyl alcohol.

milliequivalent s) The solvent feed introduced at stage 3 contained: 16.8.g'rairis KCl (225 milliequivalents) 100 grams water 50 grams isopropyl alcohol 50 gramsm'e'thanol.

The product streams were analyzed after the second cycle and the results are set forth and compared to the feed streams in the table below.

The results indicate that the 3-stage operation was effective in separating NH,+ and K+ cations, although additional stages would be required to obtain substantially complete separation. The 2 cycles had not been enough to bring the system to a steady state. Nevertheless, the example demonstrates the suitability of a mixture of methanol and isopropyl alcohol as solvent.

Composition of light Composition of heavy The conversion of potassium chloride and diammonium phosphate to potassium phosphate and ammonium chloride was elfected in a set of seventeen separatory funnels.

' Five of the" seventeen funnels constituted a S-stage phosphate stripping section. The remaining 12 funnels formed a l9-stage reaction section and a 3-stage chloride'stripping section. A singlestage consists in thorough mixing of two the layers.

Startup of reaction section.Operation was begun without stripping sections, using feed solutions that included not only diammonium phosphate and potassium chloride,

. but also estimated quantities of salts that would be re turned to the reaction section by the strippers. These feeds were:

Pv feed-left end:

4.4 grams (NH HPO 1.8 grams NH CI 17.0 grams H O Q feed-right end:

. 5.0 grams KCl 2.9 grams K- HPQ, 63.0 grams H O 40.0 grams isopropyl alcohol.

A row of 10 empty separatory funnels was set up, with the position (not the funnels themselves) lettered A to J from left to right. To start the operation, P feed and Q feed were mixed in the funnel in A position. After layer i 1 a layer at J was taken as a sample, and so was the top layer remaining at A. 'Because the funnel at A was now empty,

it was rinsed out, drained, and then placed at position I after each of the other funnels had been moved one place to the left. The operation was continued with additions of feed P at A, and feed Q at J, and concurrent removal top layers at A and bottom layers at J.

Startup of chloride stripping section-Two funnels were added to the '10 in the reaction section, and two new places, K and L, were designated to the right of J. These were added on, by manipulations similar to those used in startup of the reaction section. Charges were as follows Feed Q was replaced by feed Q containingi H 2.5 grams KCl 8.8 grams H O.

35.8 grams isopropyl alcohol 40.3 grams H O.

The lower layer from J was moved to the funnel at K, and the lower layer from K was taken as product.

Startup of the phosphate stripping section.II'he five funnels in the phosphate stripping section were kept in fixed positions, marked V-Z, to the left of the'reaction section. These were used as two sets, V-X-Z and W-Y. Once the startup had been completed, operations were carried out as follows:

Bottom layers from funnels W and Y were transferred to funnels X and Z, respectively. (Only 35 to 37 grams of lower layer from W was transferred; the remainder was left in the funnel.) Top layers from funnels Wand Y were transferred to funnels V and X. A simulated reflux was added to funnel V. This comprised:

1.8 grams NH CI 7.2 grams H O 15.5 grams isopropyl alcohol.

To funnel Z was added the upper layer taken from the reaction section at A, together with 104 grams of isopropyl alcohol. Hexane was added to each of the three funnels to cause separation into two layers.

Funnels V-XZ were shaken and layers allowed to sepa-' rate. The upper layer from V was taken as ammonium chloride solution,'and the bottom layer from Z was transferred :to the reaction section at A. Bottom layers from funnels V and X were transferred to W and Y, respechexane are 9 grams at V, none at W, 3 grams at X, 7 grams at Y, and 23 grams at Z. Integrated operation of the entire countercurrent extraction.0peration of the phosphate section (V-Z) was coordinated with that of the reaction section and chloride stripper, (AL) which worked as a unit. Feed P to the funnel at A was changed to feed P comprising.

2.2 grams diammonium phosphate 3.3 grams H O The other salts that had been in feed P were provided in the return stream from funnel Z.

A complete cycle for the reaction section and chloride stripper comprised the folowing steps.

(a) Add feed S (water and isopropyl alcohol) to funnel at L. ('13) Move the upper layer from the funnel at A into the Z funnel of the phosphate stripper. (c) Remove empty funnelfmm A and drain it.

20 (d) Shake each funnel at positions B to L and move one jspace to the left (positions A to K). I (e) Move'ea'ch bottom layer one space to the right. Bottom layer at Kis taken as product. I a (f) To funnel at A, add feed P (diammonium phosphate solution) and the return stream from funnel Z.

(g) To funnel at I, add feed Q (potassium chloride solution).

(h) Place empty funnel (step (c)) at L.

(i) Shake funnels at A to K.

(j) Move bottom layers one space to right.

Twice in the cycle, all eleven filled funnels are shaken, giving 22 mixing stages. At (d), nine are ascribed to the reaction section and two to chloride stripping. At (i), ten

are ascribed to the reaction section and one to chloride stripping. For each of these cycles, a complete cycle is run in the phosphate stripping section.

Results.-After 25 cycles had been run, the V-upper and K-lower layers were analyzed with results shown below. Errors in the material balance are considered to be due partly to losses in'repeated handling of the layers. Such losses would not be expected withuse of commercial extraction equipment.

' V-upper K-lower (NH4C1 (KzHP04 1 solution) solution) Layer weight, grams 251. 8 6. 9 Ion concentrations, milliequivalents per 100 grams: NHr 28. s 17. s 2. 06 289.3 29.5 0.0 HPOr 0.085 307. 1 Ions, milliequivalents in layers:

NHr 72.5 1.2 5.2 I 20.0 74.3 0.0 0.2 21.2

98 2 21 79 100 0 E 1 1: ti 1 99 DIVE. en 1'8 052 4.0 q 93/7 6/94 Cl-IHP o4- 99. 7/0. 3 0 100 Example 32 Potassium chloride was caused to react 'with an aqueous solution of an ammonia neutralized superphosphoric acid. The preparation of polyphosphates is described in numerous patents including US. Pats. 3,015,552; 2,999,010

\ perphosphoric acid (hereinafter called ammonium superphosphate) employed herein was a fertilizer of 1034- 0 grade, containing 10 percent nitrogen and-34 percent P 0 Approximately 51. percent of the P 0 was in forms other.

than orthophosphate, predominantly pyrophosphate, but

including some tripolyphosphate and a small amount of tetrapolyphosphate. Thus, the various ammonium salts listed above were present and were reacted with KCl. The desired product was a phosphate solution in which most of the ammonium ions were replaced by potassium ions. The by-product was a solution of ammonium chloride.

funnels were used, 5 (called V-Z) in the phosphate and British Pat. 1,036,544. The ammonia neutralized sustripping section, 5 (A-E) in the reaction section, and 3' and lower layers. The upper layer was moved to funnel B,

where it was mixed with a mixture of 25 meq. NNH Cl, 75 meq. ammonium superphosphate, 16 g. water and isopropyl alcohol. The lower layer was mixed in funnel D with 75 meq. KCl, 25 meq. ammonium superphosphate, 64.3 g. water and 36 g. isopropyl alcohol. The upper layer from D and the lower from B were mixed in C. The upper layer from B and the lower layer from D were used to start funnels A and E in the same way. Composition of the layers during startup is not critical because system is later operated to reach steady state.

Startup of chloride stripping section.-The chloride stripping section was built up from a temporary funnel E containing a solution containing 100 milliequivalents of KCl and 100 milliequivalents of ammonium superphosphate in 68 g. water and 1 g. isopropyl alcohol. This solution simulated the lower layer from funnel D.) By adding a I solution of 25 milliequivalents of ammonium superphosphate in 43.5 g. of water and 36.2 g. isopropyl alcohol, a new lower layer was obtained and placed in funnel F. This was treated with another portion of the same ammonium superphosphate solutioiggiving a lower'layer' to be placed in the G funnel. The series was extended to the H funnel in the same way.

Startup of phosphate stripping section-The phosphate stripping section was started by adding a solution of 100 milliequivalents of NH C1 in water and isopropyl alcohol in V and in X, while Z received a solution of 33 milliequivalents of ammonium superphosphate, 75 milliequivalents of NH Cl, and 25 milliequivale'nts'of KCl. The size of lower layer in each funnel was adjusted to 20-30 g. by adding small amounts of hexane.

The reaction and chloride stripping sections were started separately'and then integrated. At this time, operation of the phosphate stripping section was begun as described above and immediately integrated with operation of the reaction section.

Integrated operation of the entire countercurrent extraction.nce the operation has been set up, and funnels of set W-G have been filled and shaken, it proceeds as follows: the bottom layers are moved one place to the right in the alternate set, i.e., W to X, Y to Z, and so on to G to H. The upper layers are moved one place to the left, i.e., W to V, Y to X, and so on to G to F. Thus, two layers are moved into each funnel, X-Z-B-D-F, and one into each funnel V and H. Funnel V also receives feed R, a simulated ammonium chloride reflux:

1.34 grams NH C1 (25 milliequivalents) 12.9 grams H O 15.6 grams isopropyl alcohol.

Hexane (about 4-10 g.) is also added as needed to funnels V, W, and X to give bottom layers of 29-30 g. About 14 g. hexane is added to funnels Y and Z to give bottom layers of 21 and 17 g., respectively. Funnel H receives feed S:

43.5 grams H O 36.3 grams isopropyl alcohol.

as ammonium chloride'solution. Each funnel of the set' W-G receives two layers. In addition, funnel A receives feed P and funnel E receives feed Q.

Feed P:

7.0 grams 1034-() solution containing 50 milliequivalents of ammonium superphosphate. Feed Q:

3.7 grams KCl (50 milliequivalents) 18.7 grams H O.

Quantities of salts fed at each cycle were:

, 50 milliequivalents (3.7 grams) KCl 50 milliequivalents ammonium superphosphate in 7.0

grams 10-34-0 solution 25 milliequivalents (1.34 grams NH C1).

After 6 cycles of integrated operation, the V-upper and H-lower layers were analyzed with results shown below.

V-upper H-lower (NHCI (K phosphate solution) solution) Layer weight, grams 263. 0 12. 1 Ion concentrations, milliequivalents per 100 grams:

NHH' 23. 6 91. 0 4. 0 292. 0 30. 4 2. 0 0. 0 381. 0

15 77 99. 8 0. 2 Phosphate 100 Equivalent ratio NH4 11* 86/14 24/76 Cl'lphosphates 100/0 0. 5/99. 5

Example 33 2KCl+ NH 00 K CO' NH Cl I This example was started up and operated in the manner described in Example 24, using the reactants KCland (NH CO but modified to 5 reaction stages numbered 1 to 5, and no actual stripping sections.-

The aqueous contained:

72 milliequivalents (3.8 grams) of NH Cl 108 milliequivalents (4.2 grams) of (NH CO 77 milliequivalents (1.3 grams) of free NH;, 10.3 grams of water.

The organic solvent feed which was introduced at stage 5 contained:

milliequivalents (6.7 grams) of KCl 60 milliequivalents (4.1 grams) of K CO 447 milliequivalents (7.6 grams) of free NH 63 grams water.

This reaction was carried out to demonstrateapplica bility of the process of this invention as a means for manufacture of'K COg. While' the "example is limited to a reaction section, the feeds thereto included not only the reactant (NH CO and KCl but the quantities of NH CI and K CO which would be returned to thereactor when operated in conjunction with chloride and carbonate stripping sections. Free ammonia was added to maintain the (NH CO present in this form and prevent its conversion to NH HCO The content of the resulting product streams'is set forth in the table below. Comparison of the content of the' reaction is proceeding in the desired direction.

feed which was introduced at stage 1 Composition of light,

organic solvent Composition of heavy rich phase water rich phase With- Intro- With- Introdrawn at duced at drawn at duced at stage 1 stage 5 stage 5 stage 1 Total quantity of ions (milliequivalents):

NHA 161 20 180 16 150 136 0 97 9O 69 72 81 60 86 108 Water (g.) 47 63 26 10. 3 Isopropyl alcohol :(E%.)(. 92 95 3 0 N 3 milk 'e uivalents)..--fi 362 447 90 77 Distribution, percent of total of each ion (in milliequivalents) in each phase:

N H e 89 0 11 100 K*.. 10. 100 89. 5 0 Cl- 58. 5 46 41. 5 44 C08--- 4.8. 5 36 51. 5 64 Equivalent ratios:

H4 91/9 0/100 13/87 100/ CllCOa' 55/45 60/40 44/56 40/ 6 The compositions of the extract and raflinate products streams are shown graphically in FIG. 6, in comparison with the 1 stage reaction of Example 16.

The results show quite good separation of the NH,+ and K+ ions in the 5 stages, i.e., 91% of the cations in the extract, (organic-rich layer) was NH and 87% of the cations in the rafiinate (water-rich layer) were K+. Nevertheless, it may be desirable to achieve even greater separation, e.g., in excess of 95% for each of these quantities, in which case it is indicated that some 5 or more additional stages would be needed. There has been only limited separation of the Cl and CO ions (55% Clin extract and 56% CO in rafiinate), but this separation is not primarily effected in the reactor, but in the attached CO and Clstripping reactions Where substantially complete separation can be obtained in 3 to 5 stages in each.

EXAMPLE 34 This example demonstrates that the process can be operated advantageously at temperatures above ambient temperatures.

2KCl+Na HPO KgHPO +2Nacl Disodium phosphate was reacted with KCl in accordance with the above equation. This reaction was carriedout as described below with the reaction temperature maintained at about 50 C. throughout the operation. As a further modification of the process, solid NaCl was used to supply reflux and form the desired amount of aqueous phase in the system. Thus, in steady state operation, all or substantially all of the solvent and water may be added at one end of the extraction system.

Startup procedureqA set of 9 separatory funnels were used. These were divided into two groups, A-C-E-G-I and B-D-F-H, which were filled alternately.

The extraction system was started by adding to funnels A-C-E-GI the quantities of materials indicated below.

Amount in funnel Material A C E G I alents, was added to funnel B to maintain an adequate lower layer during startup. 7

Integrated operation of the entire countercurrent extraction.-- Once the initial operation had been set up and funnels B-I-I had been filled and shaken, the operation was as follows: The bottom layers were moved one place to the right in the alternate set of funnels, i.e., B to C, and so on to H to I. The upper layers were moved one place to the left. Thus, two layers were moved into each funnel, C -E-G and one into each funnel A and I. Funnels A and B each also received about 42 milliequivalents NaCl to adjust the bottom layers to the proper size (about 35 grams). Also funnel I received feed consisting of grams isopropyl alcohol and 100 grams water. In addition, funnel C received 50 milliequivalents Na HPO and the funnel G received 50 milliequivalents KCl. After shaking the funnels, layers were allowed to'form, thus completing the cycle. Operation was continued for 10 cycles.

Quantities of materials fed at each cycle were substantially as follows:

K milliequivalents 50 Na milliequivalents 134 Cl-, milliequivalents 134 (HPO milliequivalents 50 Isopropyl alcohol, grams 100 Water, grams 100,

After 10 cycles of integrated operation, the A-upper and I-lower layers were analyzed with results shown below.

A-upper I-lower (N 3.01 (KzHP O 4 solution) solution) Layer, weight, grams 196. 5 17. 7 Amount per 100 grams:

K+, milliequivalents" 10. 5 162. 3 Na milliequivalents- 61.3 72.0 C1, milliequivalents 69. 6 2. 3 (HPO4)", milliequivalents 7. 2 232. 0 Isopropyl alcohol, grams"--- 50. 4 5. 8 Water, grams 44. 1 75. 0 Ions, milliequivalents in layers K 20. 6 28. 7 N a 120. 5 12. 7 Cl- 137. 0 0. 4 (HPO4)- 4. 3 41. 0

The lower layer from I contained most of the potassium and phosphate fed to the system and would be useful for preparing a fertilizer.

SEPARATION OF SALT MIXTURES Example 35 This example illustratesv the separation of a mixture of diammonium and dipotassium phosphates from a mixture of the corresponding chlorides and does not involve a reactor section with split or remote salt feeds.

Extraction test.An extraction test was made in which portions of an aqueous. salt solution containing NHJ, K+, Cland HPO ions were treated countercurrently with portions of a solvent consisting of isopropyl alcohol and water. The extraction system consisted of eight separatory funnels used as mixer-settler units. The salt solution was fed to No. 5 funnel, the solvent mixture was fed to No. 8 funnel and the raffinate (aqueous solution) was drawn from No. 8 funnel. The extract from No. 1 funnel was the product extract. The extraction system was started up by adding the salt solution consisting of 112.5 milliequivalents of KCl, 112.5 milliequivalents of and 62.3 grams water, and solvent consisting of 51.1 grams of isopropyl alcohol and 25.6 grams of water to No. 5 funnel, mixing, then separating the phases, moving the lower aqueous layer to No. 6 funnel and the upper layer to No. 4 funnel. In the succeeding steps the same amount of salt solution was fed to No. 5 funnel and the same amount of solvent was added to No. 6 funnel, then No. 7, then No. 8 funnel. Afterthe third feed cycle, ex-

Knock- 26 tions o'f read; the product streams were analyzed. The results are s u mmarized below:

Extract Raflinate 5 Weight, grams.,.. 265. 8 56. 1 Water, wt. percent 50. 8 69. 5 Isopropyl alcohol, wt. percent- 47. 4 3. 6 Toluene, wt. percent 1. 3 Ohlorlde, meq.. 93 40 Phosphate, ,meq- 43 197 K, men 104 122 NH4, meq 93 115 Volume, ml 70 -88 I 18.2 154 Weight, gramsnl. 78.4 76,7 14.2 141 Water, wt. percent 79. 7 33. 49.5, Isopropyl alcohol, wt. percent 43. 1 1 Toluene, wt. percent 1. 3 Chloride, wt. percent. 2. 39 I 75 Chloride, meq.. 112.5 95. 3.5 PzOujwt. percent 7 r 0.53' 17.6 c P205, meq--- 112. 21. 5 81. 6 K, Wt. percent 1. 53 9. 94

meq 1 112,5 55.2 11.9,v NH4,wt. ercent t NH4, meq ju 112. 5 61.- 3 43. 2

The equivalent ratios 'in products are as follows:, I,

Extract Raflinete NH K 53/47 51/49 4 82/18 4/96 Example 36 This example illustrates the separation of a mixture of diammonium and dipotassium phosphates from a mixture of the corresponding chlorides and does not involve a reactor section with split or remote salt feeds.

Extraction test.--An extraction test was made in which portions of an aqueous salt solution containing NH K+, Cland I'IIPO4= ions were treated countercurrently with portions of solvent consisting of isopropyl alcohol and water. The extraction system consisted of three separatory funnels used as mixer-settler units. The salt solution Was fed to No. 2 funnel, the solvent mixture was fed to No. 3 funnel and the rafiinate (aqueous solution) was drawn from No. 3 funnel. The extract from No. 1 funnel was the product extract. The extraction system was started up by adding the salt solution consisting of 225 milliequivalents of KCl, 225 milliequivalents of (NH HP'O and 125 grams water, and solvent consisting of 100 grams of isopropyl alcohol and 50 grams of water to No. 2 funnel, mixing, then separating the phases, moving the lower aqueous layer to No. 3 funnel and the upper layer to N0. 1 funnel. In the succeeding steps the same amount of salt solution was fed to No. 2 funnel and the same amount of isopropyl alcohol-water solvent was added to No. 3 funnel. No. 1 funnel was treated in a socalled knockdown step to supply reflux by adding a mixture of grams isopropyl alcohol and 3.5 grams toluene, mixing and separating the resulting aqueous phase which was returned to No. 2 funnel as reflux in the next and succeeding cycles. The test was continued to approach steady-state operation. After the addition of several portlie extract and raffinate Extract Ratfinate NHI4 /K" 47/53 48/52 Cl /HPOF 68/32 17/83 This is a two-stage extraction unit with added reflux generator based on addition of isopropyl alcohol and toluene. Since there are 2 stages including the feed stage for the chloride removal and only one stage for the phosphate removal, better separation was obtained in the raffinate. By addition of more stages above or below the food stage, composition of extract or raflinate will approach upper and lower edges of the reciprocal salt pair diagram for the system. However, products of this example are considered useful fertilizers as prepared.

I claim:

1. A method for separating a mixture of water-soluble salts into salt containing polyvalent anion and salt containing monovalent anion wherein said salt mixture contains Clanions and HPO anions; and wherein the cations of said salt mixture are NH, and K+ which comprises:

(a) introducing an aqueous solution of said salt mixture into an intermediate stage of an extraction zone containing a plurality of stages,

(b) introducing a solvent consisting essentially of Water and a water miscible organic liquid selected from the group consisting of methanol, ethanol, isopropyl alcohol, n-propyl alcohol, t-butyl alcohol, acetone, dioxane, B-ethoxyethanol, dimethyl sulfoxide, piperidine, t-butylamine, dimethylformamide at a point remote from the introduction of the mixture of salts,

(c) passing said solvent countercurrent to and in intimate contact with said mixture of salts, a sutiicient quantity of salts being maintained to cause separation of said solvent into two liquid phases, a phase rich in water and a phase rich in said organic liquid, whereby HPO is selectively extracted into the water-rich phase and Clis selectively extracted into the organic liquid-rich phase,

(d) withdrawing said water-rich phase containing HPO from said extraction zone,

(e) withdrawing said organic liquid-rich phase containing Clfrom said extraction zone.

2. A method as defined in claim 1 wherein after step (e), the additional steps of (f) passing said organic liquid-rich phaseinto a poly- 3,331,661; 1967 Bois'ton 23-300 valent anion stripping zone, 2,885,265 1959 Cunningham 23312 P (g) passing water into said golyx alent anronstrlppl ntfi 1,955,015: 1 4/ Prins et 211. 123312 R ggg g ggggg fgggiggg 11, 1, mtlmae $9 4 45 Q f"5 9 0 H (h) passing said water-rich phase into a monovalentJ r bfi 3"7'7'" 231-312 AH' anion stripping zone, ,7 I p v 3,326,667 6/1967 Rooy 23-312R (i) passing said organic liquid into said monovalent j 5/ 1935 Reich 23-300 anion stripping zone countercurrent to and in inti- 2,726,138 12/1955' "Cunningham 23-312AH mate contact with said water-rich phase, 1 1

(j) returning water containing stripped polyvalent anion frorn said polyvalent anion stripping zone to 626,641 1949 G e t Britain 23-400 the @Xtmwon Zone, 593,911 M1959; Italy. 23-31211.

('k) withdrawing stripped organic liquid-rich phase' containing monovalent anion from said polyvalent OTHER REFERENCES anion stripping zone, I (1) returning organic liquid containing stripped rnonovalent anion from said monovalent anion "stripping zone to the extraction zone. a I (m) withdrawing stripped water-rich phase containing I polyvalent anion from said monovalent anion strip- Seidell: Soc. of Inorg, and Org, Eds., vol. 1, 1919, r g i dfind 2 h pp49.and561. ,7 meoaseemcaim weremaou I to 20 parts by weight of liquid hydrocarbon per hundred G Bull' m' 1951 992 1002" parts of the mixture of water and organic solvent is intro- NORM AN'YIUDKOFF Primary Examiner dueed into the polyvalent anion stripping zone in order 25 6, N0. 6, .1une 1951. v Garwin:;,Industrial & Engineering Chemistry, vol. 49, N0. 9, September 1957, pp. 1355-1360.

to ensure the separation of the mixture into two phases.

A s an EIF eI 7.

References Cited US. Cl. X.R.

UNITED STATES PATENTS v 23-312 A, 312AH; 423-181, 321, 471, 308, 499

1,648,224 11/1927 Hall 23312R i 3,450,508 6/1969 Cooper 23312AH 7 Zharovskii et al.: .Russian Journal of Inorg. Chem, vol. 

